The direction of root growth can be studied by analyzing the trajectories of roots growing in soil. Both the primary seminal root and nodal roots of maize attain a preferred, or liminal, angle of growth that deviates from the vertical. These roots are said to be plagiogravitropic. Experiments using plants grown in soil-filled boxes revealed that the primary seminal root is truly plagiogravitropic. It shows both positive and negative gravitropism in response to gravity stimuli and tends to… CONTINUE READING